Have you any idea of customizing toolbars?
As you are calling yourself a Power User, you would be aware of customizing toolbars.
And there aren't "narrow group of people" who want the old interface back, there are "broad group of people" who want it back.
You are technically right about navigating the ribbon but compare it with navigating customized toolbars. Ribbon is no-where near it.
Ms Office' menus are never deeper than 2 levels and on the 2nd level too, there aren't tools which are used most often. And if a tool is often used which is at 2nd level deep in the menu, again, Office 2003 has the toolbar customization facility.
Developers do not need to write extra code for toolbar when ribbon is also implemented because toolbars were already there in Office. They may have to write new code for the ribbon.
People want to try/use new things and want to have new features but not at the cost of current flexibility.